With fewer air traffic controllers at the helm, that would mean airlines would have to reduce the number of flights in and out of each airport. Fewer flights would mean delays of up to 90 minutes at some airports, LaHood said.

But some of the top Republicans in Congress dealing with transportation issues now say they're skeptical. "This is a false alarm," Rep. Bill Shuster, who heads the House Transportation and Infrastructure Committee, told Fox News Tuesday. "There is no financial data to back this up. There’s plenty of money there. They need to sharpen their pencil."

Shuster and Sen. John Thune, ranking member of the Senate Commerce, Science and Transportation Committee, are seeking answers from LaHood. In a letter they sent him Monday and released Tuesday, they asked for details on how the FAA will spend it money, on a month-by-month basis, if the sequester happens.

Shuster and Thune maintain that the administration hasn't actually produced any data to support LaHood's dramatic conclusion that Americans could start to experience delays at the airports soon after the March 1 deadline passes.

Some budget experts say that federal agencies could avoid the cuts by scheduling them for the end of the fiscal year, in hopes that the sequester would be reversed before the cuts would have to actually be implemented.

But LaHood has insisted his hands are tied. "(T)he idea that we’re just doing this to create some kind of a horrific scare tactic is nonsense," LaHood said last week.